Optical payload with folded telescope and cryocooler

ABSTRACT

A compact optical payload for an unmanned aircraft includes two infrared cameras for wide and narrow field viewing, a daylight color camera, a laser pointer and a laser range finder.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application claims priority under 35 U.S.C. 119(e) to ProvisionalApplication Ser. No. 61/127,320 by McKaughan et al, filed on May 12,2008, which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under U.S. Army contractno. W15P7T-04-C-K447. The Government of the United States of America mayhave certain rights to this invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical payload configured to becarried by an Unmanned Airborne Vehicle (UAV) conforming to Class II UAVstandards. In particular, the payload includes two or more video camerasand electrical systems suitable for combining video images from twocameras into a single network packeted data stream. A primary videocamera includes a folded telescope and a folded cryocooler to reduce avolume footprint of the optical payload. A laser rangefinder and lasertarget designator share a large aperture telescopic lens system tofurther reduce a volume footprint of the optical payload. A hollowcylindrical yoke assembly houses circular PC boards to further reduce avolume footprint of the optical payload.

2. Description of the Related Art

Optical payloads for airborne reconnaissance are described in the patentliterature. One example system is disclosed in U.S. Pat. No. 5,005,083by Grage et al. which describes a dual channel camera having wide andnarrow fields of view and electrical systems suitable for tracking atarget and for combining full image information from both fields of viewin a single picture using a mixing device. However, Grage et al. issilent as to whether the two cameras have different spectral ranges, asto the specific camera or pointing platform designs, or as to whetherthe system includes an incorporated laser range finder or laser targetdesignator.

Another optical payload system is disclosed in U.S. Pat. No. 6,410,987by O'Neil which describes a video imaging system that includes wide andnarrow field of view lens systems each forming an image of a target areaonto the same infrared sensitive focal plane array. The system includesa movable mirror disposed to direct either the wide field of view or thenarrow field image of the target area onto the infrared sensitive focalplane array, but not both. The infrared sensor is a two-color sensorhaving two regions with a first region sensitive to a first infraredwavelength range and a second region sensitive to a second infraredwavelength range. The system includes a dichroic beam splitter disposedbetween the movable mirror and the two-color focal plane array fordividing the image of the target area into two color images. Thedichroic beam splitter splits the image of the target image area intotwo color images and directs a first color image onto the first focalplane array region sensitive to the first infrared wavelength range anddirects the second color image onto the second focal plane array regionsensitive to the second infrared wavelength range. However, O'Neil doesnot teach an optical payload that utilizes a plurality of focal planearrays with different spectral sensitivity ranges or an optical payloadthat is capable of rendering and simultaneously displaying video imagesof the target area over two different fields of view and over twodifferent spectral ranges.

One example of an optical payload that incorporates a laser rangefinderand a laser target designator and uses a single large aperture opticalsystem to perform multiple tasks is described in U.S. Pat. No. 6,903,343by Amon et al. which describes a payload having a wide field of viewsmall aperture optical system and a narrow field of view large apertureoptical system wherein the large aperture optical system is used tocollect energy from a target area to provide a narrow field of viewimage of a target area focused on a first detector, and an image of alaser designator spot formed on the target area also focused onto afirst detector. However, the Amon et al. disclosure does not teachincorporating laser range finder and laser target designator emittersinto the optical payload.

There is a need to reduce the size and weight of camera systems used onUnmanned Airborne Vehicle (UAV). More generally, there is a need tofurther integrate optical payloads to provide increased functionality,reduced weight and improved aerodynamic performance without sacrificingimage quality or decreasing the useful range of the device. It is alsouseful to allow a user to view two images simultaneously such as a lowmagnification image of the target area to provide situational awarenessand a high magnification image of a selected target within the targetarea. Moreover UAV payloads may require a visible camera to providecolor day image in daylight so that target areas are more recognizableto a remote operator. This is not usually required in a manned aircraftsince the aviators are able to see the target area in daylight. Thepresent invention remedies the problems encountered in the prior art.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present invention is directed to an opticalpayload for directing a primary pointing axis at a target areacomprising a primary video camera and a folded cryocooler formedintegrally with the primary video camera for cooling a primary focalplane array to an operating temperature below 90° K. The primary videocamera includes a folded narrow field of view fixed magnificationtelescopic optical system for forming a primary image of the target areaonto the primary focal plane array at a first magnification. The primaryfocal plane array comprises elements suitable for rendering a primaryvideo image over a mid-infrared spectral range.

Another embodiment of the present invention is directed to an opticalpayload for directing a primary pointing axis at a target areacomprising a primary video camera, a folded cryocooler formed integrallywith the primary video camera for cooling a primary focal plane array toan operating temperature below 90° K, a secondary video camera and thirdvideo camera. The primary video camera includes a folded narrow field ofview fixed magnification telescopic optical system for forming a primaryimage of the target area onto the primary focal plane array at a firstmagnification. The primary focal plane array comprises elements suitablefor rendering a primary video image over a mid-infrared spectral range.The secondary video camera includes a fixed magnification wide field ofview optical system for forming a secondary image of the target areaonto a secondary focal plane array at a second magnification that isless than the first magnification. The secondary focal plane arraycomprises elements suitable for rendering the secondary video image overa long-infrared spectral range. The third video camera includes anoptical system for forming a tertiary image of the target area, whereinthe tertiary video image of the target area is in a visible spectralrange.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention will best be understood from adetailed description of the invention and a preferred embodiment thereofselected for the purposes of illustration and shown in the accompanyingdrawing in which:

FIG. 1 is an exploded isometric view depicting elements of an opticalpayload according to the present invention.

FIG. 2 is an exploded isometric view depicting further elements of anoptical payload according to the present invention.

FIG. 3 is a front isometric view depicting an optical bench assemblyaccording to the present invention.

FIG. 4 is a rear isometric view depicting an optical bench assemblyaccording to the present invention.

FIG. 5 is an exploded isometric view of an optical bench assemblyaccording to the present invention.

FIG. 6 is an exploded isometric view depicting a secondary drive andsecondary camera according to the present invention.

FIG. 7 is a schematic view depicting a combined laser rangefinder andlaser target designator according to the present invention.

FIG. 8 is a schematic plan view depicting a primary video camera forrendering an image of a target area according to the present invention.

FIG. 9 is a schematic plan view depicting a secondary video camera forrendering an image of a scene area according to the present invention.

FIG. 10 is an exploded isometric view depicting electrical subsystems ofan optical payload according to the present invention.

FIG. 11 is an exploded isometric view depicting a plurality of circularPC boards and related mounting elements according to the presentinvention.

FIG. 12 is a schematic view of video data paths through the opticalpayload according to the present invention.

FIG. 13 depicts a rear isometric view of a primary video camera thatincludes a folded large aperture telescopic lens system and a foldedcryocooler for cooling a primary focal plane array according to thepresent invention.

FIG. 14 depicts an optical schematic view of a folded large aperturetelescopic lens system according to the present invention.

FIGS. 15A and 15B depict schematic views of an optical payloadelectrical system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-5 and 10 an optical payload 100 is shown in variousviews. FIGS. 1 and 2 depict exploded external isometric views of theoptical payload 100 which includes a yoke assembly 105, configured torotate about an azimuth axis A, and a spherical payload assembly 110,supported by the yoke assembly 105 and configured to rotate about anelevation axis E. The spherical payload assembly 110 comprises anoptical bench assembly 300, shown in FIGS. 3-5, housed within aspherical housing 115. The spherical housing 115 includes opticalapertures passing therethrough and aperture windows 120 installed withineach optical aperture.

The optical bench assembly 300 includes a plurality of optical systems,detailed below, for collecting or emitting radiation through aperturewindows 120. Each optical system collects or emits radiation over afield of view defined by a solid angle centered by a central ray orwindow pointing axis 125. Some or all of the window pointing axes 125may be co-aligned along a common or primary pointing axis 130.

Referring to FIGS. 1-2 and 89 the optical payload 100 includes a primarydrive system that includes a first or azimuth drive and rotary jointassembly, generally referred to by reference numeral 135, and a secondor elevation drive and rotary joint assembly, generally referred to byreference numeral 140. The primary drive system operates to point theprimary pointing axis 130 at a target area of interest. The primarydrive system, collectively 600, includes separate and independent servocontrollers for separately controlling the azimuth drive and jointassembly 135 and the elevation drive and joint assembly 140.

The primary drive system 600 is operable in various modes such as a“search mode” to continuously scan the primary pointing axis 130 over aregion, a “manual mode” wherein a remote user can point the primarypointing axis 130 manually using a joy stick or the like, in a “scenetracking mode” wherein the primary pointing axis 130 tracks a movingtarget, in a “geo-pointing mode” wherein the primary pointing axis 130is continuously pointed at specific geographic coordinates, and mayoperate in other pointing modes.

The azimuth drive and rotary joint assembly 135 is installed within theyoke assembly to rotate the yoke assembly 105 and the attached sphericalpayload assembly 110 about a substantially vertical azimuth axis A. Theelevation drive and rotary joint assembly 140 is disposed between theyoke assembly 105 and the spherical payload assembly 110 and serves torotate the spherical payload 110 about a substantially horizontalelevation axis E. The spherical payload 110 rotates with respect to theyoke assembly 105 and with respect to a support structure 145. Each ofthe rotary joints and drives is capable of 360 degree rotation, however,in some orientations the aperture windows are vignetted by the yokeassembly 105.

The optical payload 100 is attached to the support structure 145, andthe primary drive system 600, using the azimuth and the elevationdrives, rotates the yoke assembly 105 and the spherical payload 110 topoint the primary pointing axis 130 at a scene of interest. The opticalpayload 100 includes an electrical power source and power distributionsystems, optical systems, electrical control and feedback systems, andcommunications systems as required to point the primary pointing axis130 at a target area, to render video images of the target area and totransmit the video images to a remote station for display and viewing bya user. In particular, the optical payload 100 is configured tosimultaneously transmit two video images of the scene of interest witheach video image being rendered over a different spectral range.Moreover, the communications systems may receive user generatedoperating commands from the remote station to control various modes ofoperation of the optical payload 100.

In a preferred embodiment, the support structure 145 comprises anairborne vehicle and especially an Unmanned Airborne Vehicle (UAV)conforming to Class II UAV standards. Accordingly, the preferred opticalpayload 100 is constructed with weight, volumetric footprint, andaerodynamic drag properties suitably optimized for being carried as apayload on a Class II UAV. In particular, the preferred optical payload100, excluding the support structure 145, has a design weight of lessthan 16 pounds and the preferred spherical payload assembly 110 has aspherical diameter of less than 190.0 mm and with the present examplehaving a spherical diameter of 184.0 mm, (7.25 inches).

Referring now to FIGS. 1, 2 10, 12 and 15A-B, the yoke assembly 105comprises a cylindrical top section 150 formed by a thin annular wall155 surrounding a hollow electronics cavity 160. The hollow electronicscavity 160 houses a plurality of circular printed circuit boards,(PCB's), (750, 755, 760, 765), shown in FIGS. 10 and 11, populated withsurface mounted digital and analog electrical components, electricalconnectors, forming subsystems for video processing, motor and servocontrol, target tracking, gyro stabilization, communications, cameraoperation, and the like. The hollow electronics cavity 160 also includesan upper bracket 165 that installs into a top circular opening of thecylindrical top section 150 and is attached to the thin annular wall 155for sealing the hollow electronics cavity 160, for providing structuralstiffness to the top end of the annular wall 155 and for supporting arotary interface with an azimuth hub 170.

The yoke assembly 105 includes a disk shaped azimuth hub 170 thatmechanically attaches to a support structure 145 and includes mountingfeatures, not shown, for orienting the payload assembly primary pointingaxis 130 with respect to the support structure 145. The azimuth hubfurther includes an electrical connector 175 extending upward from themounting flange to connect electrical systems housed in the payloadassembly 100 with an electrical system carried by the support structureand especially to communicate with a radio 705 shown in FIGS. 12 and15B. The azimuth hub 170 includes an external seal diameter 180 sized tomate with the upper bracket 165 at a corresponding internal sealdiameter 185 thereof. The azimuth hub 170 is fixedly attached to thesupport structure 145 by the azimuth hub 170 and the upper bracket 165is fixedly attached to the cylindrical top section 150 through the thinannular wall 155 The azimuth drive and rotary joint 135 form a rotaryjoint disposed between the azimuth hub 170 and the upper bracket 165. Inparticular, the azimuth drive and rotary joint 135 includes a rotarybearing, such as a duplex bearing set 190, for providing a rotary jointbetween the upper bracket 165 and the azimuth hub 170.

The azimuth drive includes an azimuth drive motor 195, such as a flat orpancake style motor, and a first rotary position resolver 200 suitablefor sensing a rotary position or rotation angle. The rotary positionresolver 200 may comprise an optical encoder, Hall Effect sensors, orother suitable rotary angle position transducer. In addition, theazimuth drive and rotary joint assembly 135 includes a cavity seal 205disposed between the seal diameters 180 and 185 for sealing the hollowelectronics cavity 160 from moisture and contamination. Alternately, thecavity seal 205 may be configured as a pressure seal and the hollowelectronics cavity may be filled with a pressurized gas or may beevacuated to a vacuum pressure.

The yoke assembly 105 includes opposing left and right yoke arms 210,215 extending downwardly from the top section 150. Each yoke arm 210,215 includes a hub support feature 220, 225 such as a through or blindbore, formed coaxial with the elevation axis E. The hub support features220, 225 mate with opposing left and right cylindrical mounting hubs230, (only the right hub mounting feature is shown), that extend outfrom the payload assembly 110. Referring now to FIGS. 2-6 and 10, thepayload assembly 110 comprises a substantially spherical outer housing115 sized to enclose an optical bench assembly 300, shown in frontisometric view in FIG. 3 and in rear isometric view in FIG. 4. Thespherical housing 115 comprises a front section 235 that includes theapertures and optical windows 120 and a rear section 240 that mates withthe front section 235. In addition, a pair of opposing left and rightdisk-shaped side sections, 250, only one is shown in FIG. 2, are formedto mate with the front section 235 and rear section 240 to enclose andseal the optical bench assembly 300 from moisture and contaminates.Accordingly, mating surfaces of the front section 235, the rear section240 and the left and right disk-shaped side sections 250 may be sealedby gaskets or other sealing elements or compounds applied thereon atassembly.

Preferably the yoke assembly top section 150 and left and right yokearms 210, 215 comprise a unitary machined part to increase stiffness andto meet stringent tolerance required. However, other embodiments such asa metal casting or composite structure may be used. The sphericalhousing front and rear sections 235 and 240 preferably comprise metalcastings while the left and right side section 250 are preferablymachined parts, however other embodiments are usable without deviatingfrom the present invention. Additionally, any metal casting may befurther modified by machining and other metal-forming steps to fabricatemachined features such as holes, precision mating surfaces, bearingjournals and other features as may be required. In particular, the metalcastings are formed with thin walls using lightweight, high-stiffnessmaterials comprising aluminum and/or titanium or other metals asrequired to reduce part weight without compromising structuralintegrity. Alternately, some or all of the cast elements may comprisecast or molded plastic materials such as polycarbonate, or the like, ormay comprise composite materials such as wound carbon or glass fibers,in a base of epoxy and or other bonding agents.

The disk-shaped side sections 250 support the left and right mountinghubs 230 and define the elevation axis E on the optical bench assembly300. The elevation drive and rotary joint 140 includes opposing left andright bearings 255, 260 disposed between the left and right mountinghubs 230, only one shown, and the left and right hub support features220, 225 for providing a rotary joint between the yoke arms 210, 215 andthe spherical payload assembly 110. The left bearing 255 may comprise aduplex bearing set to reduce longitudinal and axial play in the rotaryjoint.

A rotary elevation drive motor 265, such as a flat or pancake stylemotor, attaches to the left yoke arm 210 and the left mounting hub, notshown, to provide a rotary drive force for rotating the payload assembly110 about the elevation axis E and with respect to the yoke assembly 105and support structure 145. A second rotary position resolver 270suitable sensing rotary position or rotation angle, such as an opticalencoder, Hall effect sensors or other suitable angular positiontransducer, interfaces with the right mounting hub 230 and the right hubsupport feature 225 to provide an electrical signal in proposition tothe angular position of the spherical payload assembly 110 with respectto a reference angular position or orientation. A pair of cavity seals275 are disposed over the left and right mounting hubs 230 between thedisk-shaped side sections 250 and the left and right hub supportfeatures 220, 225 to seal the spherical housing 115 and the elevationdrive and rotary joint 145 from contaminates and moisture. It is aparticularly advantageous feature of each of the azimuth and elevationdrives of the present invention that both drives are rotatable over afull 360 degree angle. This is in part due to the construction ofconductive slip rings 330 for exchanging electrical signals includingelectrical power signals between electrical systems housed inside thehollow cavity 160 and electrical systems housed inside the sphericalhousing 115. The slip rings are shown in FIG. 10 disposed between theyoke arm 210 and the optical bench assembly 300. The slip rings 330include a first conductive ring fixedly attached to the yoke assembly105 and a second conductive ring fixedly attached to the payloadassembly 110. The first and second rings remain in electrical contactwith each other as the payload assembly 110 rotates about the elevationaxis E with respect to the yoke assembly 105. As shown in FIGS. 15A-B,power and electrical signals pass from electrical systems housed in theyoke assembly 105 through the slip rings 330 to the payload controller720, which is housed in the payload assembly 110 and in electricalcommunication with electrical elements of the optical payload.Similarly, electrical signals including video data pass from electricalelements of the optical payload to the payload controller 720 throughthe slip rings 330 to electrical systems housed in the yoke assembly105.

Optical Bench Assembly

Referring now to FIGS. 3-9, the optical bench assembly 300 is shown in afront isometric view in FIG. 3 and in a back isometric view in FIG. 4.The optical bench assembly 300 installs inside the spherical housing 115and comprises a rigid optical bench 305 configured to structurallysupport a plurality of optical systems thereon. Preferably the opticalbench 305 comprises a metal casting, or the like, formed with caststructural sections machined to add features such as holes and precisioninterface surfaces usable as attaching and locating features for opticalsystems. A primary video camera 310 attaches directly to the opticalbench 305. The primary video camera 310 is configured to render a videoimage of a primary target area 320 shown in FIG. 8, over a mid-infraredspectral range and a central ray of the primary camera field of viewdefines the primary pointing axis 130.

A secondary video camera 315 is mounted on a secondary drive system 400,shown in detail in FIG. 6. The secondary drive system 400 is rigidlyattached to the optical bench 305 and configured to movably support thesecondary video camera 315 for rotation with respect to the opticalbench 305 about two rotational axes. The secondary video camera 315 isconfigured to generate a video image of a target area 325 shown in FIG.9, over a long-infrared spectral range and a central ray of thesecondary camera field of view defines a secondary pointing axis 332.

The preferred optical bench assembly 300 includes a third video camera335, a laser range finder transmitter module 340 and small aperturetelescopic lens system 342 for collimating a laser transmitter beam, alaser target designator module 345 and associated large aperturetelescopic lens system 390 for collimating a laser designator beam. Eachof the third video camera 335, laser rangefinder transmitter module 340and laser target designator module 345 have a field of view and anindividual pointing axis 125, which is preferably aligned or boresighted coaxially with the primary pointing axis 130. Preferably thethird video camera 335 is configured to generate a video image of thesecondary target area 325 shown in FIG. 9, over a visible spectralrange.

Referring now to FIGS. 8 and 9, the primary video camera 310 comprises ahigh resolution, narrow field of view, (NFOV) video camera usable torender a mid-range infrared image of a primary target area 320 within alarger target area 325. More specifically, the primary video camera 310is configured to render a magnified image of a portion of the targetarea 325 and the magnified image has sufficient optical resolution toidentify a primary target from a specific range. The primary videocamera 310 includes a primary telescopic lens system 350 having aneffective focal length of approximately 200 mm and a stop aperture, orthe like, defining the NFOV, e.g. approximately encompassing a solidangle of 2.7 degrees horizontal, 360, by 2.0 degree vertical. Thecentral ray of the NFOV may define the primary pointing axis 130.Alternately, the laser target designator beam 416 may define the primarypointing axis 130, in which case other elements of the optical payloadare bore-sighted to co-align with the designator beam 416. The primaryvideo camera 310 rigidly attaches to the optical bench 305 and istherefore pointed at a desired primary target area 320 by movement ofthe primary drive system 600. Referring now to FIGS. 5, 13 and 14, theprimary telescopic lens system 350 is folded by two fold mirrors 920 and925 each disposed at a compound angle with respect to the telescopeoptical axis. In addition, an integrated Dewar and cryogenic coolermodule, (IDCA) 370 is coupled to the primary video camera 310 andsupported by the optical bench 305. The IDCA 370 cools a primary focalplane array and other local support structure of the primary videocamera to an operating temperature of approximately 77° K to reducesignal noise in the focal plane array. More specifically the IDCA 370comprises a folded compact cryocooler design such as the one disclosedin co-pending and commonly assigned U.S. patent application Ser. No.11/433,697, entitled COOLED INFRARED SENSOR ASSEMBLY WITH COMPACTCONFIGURATION, filed on May 12, 2006, the entirety of which isincorporated herein by reference. The cryocooler 370 comprises a rotaryDC motor 930 driving a gas compressor. The gas compressor is housed in acrankcase 935. The rotary DC motor 930 is also connected to aregenerator piston 940 through a folded linkage that is also housed inthe crankcase 935. Rotation of a shaft of the DC motor 930 is coupled tothe regenerator piston 940 through the folded linkage which reciprocallydrives the regenerator piston 940 along a linear axis that issubstantially parallel with the rotation axis of the DC motor 930. Thus,the folded cryocooler design reduces its longitudinal length. Accordingto the present invention, both the primary telescope 350 and the IDCA370 are folded in order to reduce the volume foot print of the primaryvideo camera 310 and more specifically, to reduce the spherical diameterof the payload assembly 110.

As shown in FIG. 14, the primary telescope 350 includes a large apertureobjective lens 905 and a plurality of focus elements 910 with some ofthe focus elements being movable along a focal plane axis 926 to adjustthe focal plane location of the lens system 350. The lens system 350further includes a conventional automated lens actuator 915 configuredto axially displace one or more of the focus elements 910 as required toadjust the position of a focal plane of the lens systems 350. Mirrors905 and 925 act to fold focal plane axis 926 with respect to primarypointing axis 130 such that focal plane axis 926 is not parallel toprimary pointing axis 130.

The primary video camera 310 includes a conventional focal plane array365, shown schematically in FIG. 8, comprising a plurality of activeimage sensors disposed over an active area which is positioned in afocal plane of the primary telescopic lens system 350 such that theprimary telescopic lens system 350 forms a focused image of the primarytarget area 320 that substantially fills the active area of the focalplane array 365. As stated above, at least one of the focus elements 910is movable by an actuator to change the position of the lens systemfocal plane with respect to the position of the focal plane array 365.The primary video camera 310 may also include an automated shutteradjusting system for varying the stop aperture size or othercharacteristics of the primary video camera 310 in order to maintainirradiance levels at the primary focal plane array 365 to within usablelimits.

The primary focal plane array 365 is configured to generate a photocurrent in response to mid-range infrared radiation falling thereon,e.g. radiation with a wavelength of 3-5 microns. More specifically, theprimary focal plane array comprises an array of 640×480 indiumantimonide (InSb) detector elements and the entire array and localsupport structure is cooled by the IDCA 370 to an operating temperatureof approximately 77° K to reduce signal noise in the focal plane array.

Secondary Camera

The secondary video camera 315 comprises a wide field of view, (WFOV)video camera usable to render a long-range infrared image of the targetarea 325. More specifically, the secondary video camera 315 isconfigured to render an image of the target area 325 with sufficientoptical resolution to detect the presence of a target from a specificrange. The secondary video camera 315 includes a secondary telescopiclens system 375 having a fixed magnification and an effective focallength of approximately 25.0 mm and a stop aperture, or the like,defining the wide field of view, e.g. approximately encompassing a solidangle 380 of 35 degrees horizontally and a solid angle of 27 degreesvertically. The central ray of the WFOV defines the secondary pointingaxis 332. The secondary drive system 400 is disposed between the opticalbench 305 and the secondary video camera 315 for rotating the secondaryvideo camera 315 with respect the optical bench 305.

The secondary telescopic lens system 375 comprises a two germaniumelement fixed field of view lens system. A secondary focal plane array385 shown in FIG. 9, comprising a plurality of active image sensorsdisposed over an active area and is positioned in a focal plane of thesecondary telescopic lens system 375 such that the secondary telescopiclens system 375 forms a focused image of the target area 325 that fillsthe active area. The secondary video camera 315 may also include anautomated shutter adjusting system for varying the stop aperture size inorder maintain irradiance levels at the secondary focal plane arraywithin usable limits as well as for closing the shutter to perform afocal plane array response uniformity calibration.

The secondary focal plane array 385 is a microbolometer resistancechange device configured to generate a photo current in response tolong-range infrared radiation falling thereon, e.g. radiation with awavelength of 8-12 microns. More specifically, the secondary focal planearray comprises an array of 640×480 silicon detector elements operatingat ambient temperature.

Color Day Camera

The third video camera 335 comprises a visible wavelength video cameraor color day camera usable to render a color image of the target area325 in the visible spectrum, e.g. radiation with a wavelength range of400-700 nanometers. The color day camera 335 includes a fixedmagnification visible lens system 392 having an 8 mm effective focallength and a field of view approximately encompasses a solid angle 380of 35 degrees horizontally and 27 vertically. The visible lens system392 is a fixed focal length lens system and is positioned to form asubstantially focused image of the target area 325 onto a color dayfocal plane array, not shown, such as a conventional visible colorsensitive charged coupled device (CCD). The color day camera 335 alsoincludes automated systems for varying its configuration and operatingmode according to irradiance levels at the CCD in order to generate auseful image over a wide range of daylight light levels. In particular,the third video camera 335 may comprise a camera model 20K155DIG sold byVIDEOLOGY of Greenville R.I., USA, or a camera model KPC-520C sold byKT&C of Seoul, South Korea.

LR/D

Referring now to FIGS. 3, 5 and 7, a laser rangefinder system comprisestwo elements separately disposed within the payload assembly. A firstelement comprises a laser rangefinder transmitter 340 for transmitting alaser rangefinder beam 425. A second element comprises a laserrangefinder receiver 430 disposed inside a laser designator module 345.The laser rangefinder receiver 430 is disposed inside the laserdesignator module 345 to utilize its large aperture telescopic lenssystem 390 which it shares with the designator laser 346.

The laser target designator module 345 comprises a designator laser 346and laser pumping elements, not shown. Preferably, the designator laser346 is configured as a pumped neodymium YAG solid state laser operatingto emit radiation pulses at a radiation wavelength of approximately 1064nanometers. Preferably the designator laser 346 generates pulses havinga minimum duration of 10 nanoseconds modulated at a frequency of 10-20pulses per second with a pulse energy of greater than 30 mJ. Preferablythe designator laser 346 is pumped by a laser diode; however, otherpumping sources such as flash lamps are usable. Pulses emitted by thedesignator laser 346 pass through a beam splitter 415 and are directedby mirrors 410 through the large aperture telescopic lens system 390 togenerate a substantially collimated designator beam 416. Preferably thebeam splitter 415 is a dichroic filter configured with a high spectraltransmittance substantially centered at the output wavelength of thedesignator laser which is approximately centered at 1064 nanometers. Inthe present example embodiment, the laser target designator module 345is fixedly mounted to the disk shaped side section 250. Optionally, thelaser target designator module 345 may be mounted to the optical bench305. In either case, the orientation of the laser target designatormodule 345 is adjusted to coaxially align a pointing axis of thedesignator beam 416 with the primary pointing axis 130. Alternately, thedesignator beam 416 may be used as the primary pointing axis 130 withother elements of the optical payload being bore-sighted to co-alignwith the designator beam 416. Accordingly, the laser designator beam 416may be used to illuminate target areas being imaged by the primary videocamera 310. The large aperture telescopic lens system 390 is configuredwith a large aperture, e.g. 50-90 mm, to produce a designator beam 416having a large enough diameter to produce a desired low beam divergenceangle while the designator laser 346 is designed with laser radiationenergy output levels as required to illuminate a desired target size ata desired target range.

The laser rangefinder transmitter module 340 comprises a compact pulsedrangefinder laser 341 such as an Erbium (Er) glass laser pumped by alaser diode and operating to emit radiation pulses at an eye-saferadiation wavelength, i.e. a range of 1500 to 1800 nanometers.Preferably the laser 341 generates laser pulses having a wavelengthapproximately centered at 1535 nm with pulse durations ranging from 5 to25 nanoseconds and with a pulse energy ranging from 2 to 8 mJ. The laserrangefinder transmitter module 340 further includes a small aperturetelescopic lens system 342 suitable for generating a substantiallycollimated rangefinder beam 425. The rangefinder laser transmittermodule 340 is fixedly attached to the optical bench 305 and adjusted tocoaxially align a central ray of the collimated rangefinder beam 425with the primary pointing axis 130 such that the laser rangefinder beam425 is directed at the target area 320 and is pointed by the primarydrive system 600.

After reflecting from a target area, a portion of the energy of thelaser rangefinder beam 425 is reflected back to the optical payload 100and collected by the large aperture telescopic lens system 390. Thereflected energy is directed onto a laser rangefinder receiver module430, by the mirrors 410 and the beam splitter 415. Accordingly the beamsplitter dichroic filter is further configured with a high spectralreflectance substantially centered at the output wavelength of therangefinder laser 341, which is approximately centered at 1535nanometers. The collection optics further include a focusing lens set420 that focuses the collected energy onto an active area of therangefinder receiving module 430. The rangefinder receiving module 430comprises a pin diode or the like, which generates a photocurrent inresponse to radiation falling thereon. The photocurrent is communicatedto a signal process 424 for digital signal processing.

The combined laser rangefinder module 340 laser target designator module345 further includes a fiber optic element 422 that extends between therangefinder laser 341 and the laser target designator module 345. Afirst end of the fiber optic element 422 is disposed inside therangefinder laser 341 at a location that couples a portion of the energyof each rangefinder laser output pulse into the first end of the fiberoptic element 422. A second end of the fiber optic element 422 isdisposed inside the laser target designator module 345 at a locationthat directs energy being emitted from the second end of the fiber opticelement 422 onto receiver module 430 and particularly at the active areathereof. Accordingly, the fiber optic element 422 directs rangefinderlaser output pulse energy onto the receiver module 430 and the photodiode generates a photocurrent responsive to each rangefinder laseroutput pulse. The photocurrent is communicated to a signal processor 424for digital signal processing. The processor 424 is included on thepayload controller 720.

Accordingly, the signal processor 424 processes first signals responsiveto each output pulse of the rangefinder laser 341 and second signalsresponsive to each rangefinder laser pulse that is reflected back fromthe target area. Generally the signal processor 424 calculates a rangefrom the target area to the optical payload 100 according to a temporalseparation between output pulses of the rangefinder laser 341 andrangefinder laser pulses that are reflected back from the target area.The calculation may be made using clock signals generated by the signalprocessor 424 or by another signal processor to determine the temporalseparation.

Specifically according to the present invention, by sharing the largeaperture telescopic lens system 390 between the laser target designatormodule 345 and the laser rangefinder transmitter module 340, the volumefootprint of the combined laser target designator and laser rangefinderis reduced in order to reduce the spherical diameter of the payloadassembly 110. Moreover, a second benefit is gained by sharing the largeaperture telescopic lens system 390 between the laser target designatorand the laser rangefinder. Specifically, the large aperture telescopiclens system 390 collects more radiation energy from the target area thancan be collected by a smaller aperture telescope, e.g. the smallaperture telescopic lens system 342, such that by collecting laserrangefinder beam energy reflected back from the target area with thelarge aperture telescopic lens system 390 the useful range of the laserrangefinder is increased. According to the invention, the aperturediameter of the large aperture telescopic lens system 390 is selected asrequired to collimate the target designator beam 425 with a divergenceangle that is small enough to illuminate a target of a specific size ata specific maximum range. However, since the large aperture telescopiclens system 390 is used to collect reflected laser rangefinder energy,the maximum range of the laser rangefinder is increased as well.

Secondary Drive.

Referring now to FIG. 6, the secondary video camera 315 and elements ofthe secondary drive system 400 are shown in exploded isometric view. Thesecondary drive 400 comprises a pivot bracket 440. The pivot bracket 440is a solid unitary structural member, such as a metal cast element,having a top arm 445, and a pair of opposing side arms 450, 455extending substantially orthogonally from the top arm 445.

The top arm 445 includes a mechanical coupling 460 fixedly installedtherein such as by a press fit. The mechanical coupling 460 is formed byan annular wall surrounding a longitudinal bore 465. The bore 465 isoriented substantially parallel with the azimuth axis A. A secondaryazimuth motor 470 comprises a motor body 475 and a rotatable drive shaft480 extending out there from. The rotatable drive shaft 480 installsinto the bore 465 and is fixedly coupled to the mechanical coupling 460.The motor body 475 is fixedly attached to the optical bench 305. A drivecurrent applied to the secondary azimuth motor 470 causes the rotatableshaft 480 and the pivot bracket 440 to rotate with respect to theoptical bench 305. The rotation is about an axis that is substantiallyparallel with the azimuth axis A. The top arm 442 may include a curvedslot 442 with adjustable end stops, such as may be provided by thethreaded fasteners 485, for setting rotation end stops.

The side arms 450 and 455 each include a rotary bearing or bushing 490and 495 fixedly installed therein. Each bearing 490, 495 includes anannular wall surrounding a longitudinal bore 505 and 510. The bores 505and 510 are oriented coaxially along an axis that is substantiallyparallel with the elevation axis E when the pivot bracket 440 is at thecenter of its rotational range. The secondary video camera 315 includespivot pins 515 and 520 extending out therefrom and fixedly attachedthereto for installing into the coaxial bores 505 and 510 to therebypivotally support the secondary video camera 315 with respect to thepivot arm 440. The rotation is about an axis that is substantiallyparallel with the elevation axis E when pivot bracket 440 is at thecenter of its rotational range.

The side arm 450 is formed with a circular mounting flange 525. Theflange 525 is configured to support a secondary elevation motor 530. Thesecondary elevation motor 530 comprises a motor housing 535 and arotatable drive shaft, not shown, extending out from the motor housing.The rotatable drive shaft installs into a drive gear 545 and is fixedlyattached thereto so that rotation of the drive shaft 540 rotates a drivegear 545. The drive gear 545 meshes with a driven gear 550 which isfixedly attached to the pivot pin 515. A drive current applied to thesecondary elevation motor 530 causes the elevation motor 530 and itsrotatable shaft to rotate the drive gear 545 with respect to the sidearm 450. Rotation of the drive gear 545 drives the driven gear 550 whichcauses the secondary video camera 315 to rotate about an axis that issubstantially parallel with the elevation axis E when the pivot bracket440 is at the center of its rotational range.

The above-described rotations of the secondary video camera 315 allowthe secondary pointing axis 332 to be pointed independently from theprimary pointing axis 130. Preferably the secondary video camera 315 isrotated over rotation angles approximately limited to plus or minus onehalf the solid angle fields of view of the secondary video camera 315.More specifically, the secondary drive system 400 is initially assembledand aligned to point the secondary pointing axis 332 substantiallycoaxial with the pointing direction of the primary pointing axis 130.The secondary drive 400 is configured to rotate the pivot bracket 440and secondary video camera 315 approximately over plus or minus 20degrees using the secondary azimuth motor 470 in order to change theazimuth angle of the secondary pointing axis 332 with respect to theazimuth angle of the primary pointing axis 130. The secondary drivesystem 400 is further configured to rotate the secondary video camera315 approximately over plus or minus 15 degrees using the secondaryelevation motor 530 in order to change the elevation angle of thesecondary pointing axis 332 with respect to the elevation angle of theprimary pointing axis 130. In addition, each of the secondary azimuthmotor 470 and secondary elevation motor 530 includes an angular positionresolver included therein or otherwise associated therewith forproviding electrical signals in proportion to angular orientation of thesecondary video camera 315 or the pointing axis 332.

Referring to FIGS. 4, 9 and 10, a top view of the payload assembly 110is shown schematically to demonstrate rotation of the primary andsecondary cameras about the azimuth axis A. The description issubstantially identical for rotation about the elevation axis E exceptthat vertical fields of view may be slightly narrower for each camera.According to the present invention, the primary drive 600 operates torotate the spherical payload 110 in two axes to rotate the primarypointing axis 130 and every other pointing axis of the payload systemsimultaneously. Meanwhile, each of the three video cameras is renderingvideo images with the primary video camera 310 rendering a video imageof the primary target area 320 and the second video camera 315 and thethird video camera 335 are each rendering a video image of the targetarea 325. Thus an operator viewing the video image of the secondarytarget area 325 can detect smaller target areas 320 that may be ofinterest and direct the primary pointing axis 320 at a selected smallerprimary target area 320. Meanwhile, the secondary drive 400 may beoperated in a counter slew mode in which the secondary drive system 400is operated to offset small rotations by the primary drive system 600 byapplying equal and opposite rotations to the secondary video camera 315.The equal and opposite rotations cause the secondary pointing axis 332to remain substantially centered on the secondary target area 325thereby causing the image of the secondary target area 325 to remainsubstantially unchanged as the primary camera 310 is rotated to renderan image of the selected target area 320. In addition, the optical benchassembly 300 includes gyroscopic stabilizing elements 353, 355 operatingin cooperation with the primary drive system 600 to simultaneouslystabilize the pointing direction of the primary pointing axis 130.

Electrical Control System and FIGS. 10-12

Referring now to FIGS. 4, 10-12, and 15A-B, elements of a payloadelectrical control system 700 are shown in an exploded isometric view inFIGS. 10 and 11 and in schematic views in FIGS. 12 and 15A-B. Theelectrical control system 700 includes all the electrical systemsrequired to operate the optical payload 100 autonomously and to outputvideo and other signals to a radio 705, carried by the UAV or othersupport structure 145. The radio 705 broadcasts the output signals toone or more remote radio stations 710 and receives command and controlsignals from the one or more remote radio stations 710. As shown inFIGS. 12 and 15B, the radio 705 and remote stations 710 operate toexchange command and control signals and the radio 705 deliversappropriate command and control signals to the payload electricalcontrol system 700. In addition, each remote radio station 710 mayinclude a video display device 715 and user interface controls 721operable to view live video images received from the optical payload 100and specifically to view images from two of the three payload cameras310, 315 and 335 simultaneously. In addition, a user operating theinterface controls 721 can command the optical payload 100 remotely topoint either of the pointing axes 130 or 332 at a target area 325 or aselected target 320 and to select which two live camera images toreceive from the payload assembly and display on the video displaydevice.

The electrical system 700 is configured to continuously operate theprimary video camera 310 and to continuously deliver images rendered bythe primary video camera 310 to the radio 705 a wireless networkprotocol such as wireless Ethernet. Moreover, the images rendered by theprimary video camera are network packeted for delivery to a firstnetwork IP address associated with which ever remote radio station 710is sending command and control signals to the optical payload and morespecifically the first IP address is exclusively associated with theprimary video images.

The electrical system 700 includes a switch or multiplexer, not shown,mounted on the optical payload controller 720. The switch or multiplexeris in communication with each of the secondary video camera 315 and thetertiary video camera 335. Using the multiplexer, a user at the remoteradio station 710 can command the optical payload to operate andtransmit video images rendered by either the secondary or tertiary videocamera but not both. Once one of the secondary or tertiary cameras isselected, the selected camera is operated and the system 700 isconfigured to operate the selected video camera 315 or 335 and tocontinuously deliver images rendered by the secondary video camera 315or 335 to the radio 705 using a wireless network protocol such aswireless Ethernet. Moreover, the images rendered by the selected videocamera 315 or 335 are network packeted for delivery to a second networkIP address associated with whichever remote radio station 710 is sendingcommand and control signals to the optical payload and more specificallythe second IP address is exclusively associated with the video images ofthe selected camera.

The electrical system 700 is further configured to track video targetsin both video images being transmitted to the remote radio station 710,to determine target ranges, target geo-locations, target temperaturesand other data about the target area as may be required and to generatetarget meta data. The target meta data may comprise video overlays suchas a cursor text box and or graphical data display that is updated ineach video frame. Accordingly, the electrical system 700 is furtherconfigured to network packetize the target meta data for delivery to athird network IP address associated with whichever remote radio station710 is sending command and control signals to the optical payload.Specifically the third IP address may be used as the IP address for alltarget meta data as well as any command and control signals that areexchanged between the optical payload and remote radio station 710 issending command and control signals to the optical payload.

Generally, the electrical system 700 includes various digital processorsconfigured or programmed for video image signal processing as may berequired to correct the video signals, to make signal value offsets andgain adjustments for reducing signal noise, to adjust brightness andcontrast to desired levels, to replace dead pixels with data valuespredicted from surrounding pixel data values, and to enhance imagedetail such as by sharpening edges or the like. In addition, the videoimage rendered by each camera is scaled to a desired display format sizeprior to transmission or at the remote radio station. In the preferredembodiment, target meta data in the form of text and graphics overlaydata is not combined with the video image data in the payload but sentto the third IP address at remote station for remote combination withthe video images. However, the meta data can be combined with the videoimages by the electrical system 700. In addition, the electrical controlsystem 700 operates to compress the video data of the primary videoimage and the selected video image and to merge the two compressedimages into a single wireless network packeted data stream. Theelectrical system 700 further includes an Ethernet switch 816, whichoperates cooperatively with a communication processor 820 and the radio705. The communications processor 820 configures and routes network datapackets exiting the payload to the intended IP address as well asreceives incoming network data packets and routes the data to a mastercontroller PC board 760, described below.

The electrical system 700 further operates the primary drive system 600in a manner that directs the primary pointing axis 130 at a target area325 and at selected targets 320 and steers the primary pointing axis 130in order to keep the target area within the field of view of the primaryvideo camera 310 even as the optical payload 100 is being carried by amoving aircraft or vehicle. In addition, the electrical system 700includes gyro stabilizing elements 353 and 355, housed inside thespherical payload assembly 110, for providing gyro stabilizing signalsusable to stabilize the pointing direction of the primary pointing axis130.

The electrical system 700 further operates the secondary drive system400 in a manner that directs the secondary pointing axis 332 at a targetarea and steers the secondary pointing axis 332 in order keep the targetarea within the field of view of the secondary video camera 315 even asthe primary pointing axis is being actively pointed by the primary drivesystem 600.

As shown in FIGS. 10 and 11, the electrical control system 700 comprisesa plurality of interconnected electrical sub modules, and individualelectrical components disposed within the spherical payload assembly 110and or within the yoke assembly 105. The electrical control system 700can be mechanically divided into two portions, namely electrical subsystems housed within the spherical payload assembly 110 and electricalsub systems housed within the yoke assembly 105. The two portions areelectrically interconnected by a conventional slip ring assembly 330.The slip ring assembly 330 is included as a component of the elevationdrive and rotary joint 140 and provides opposing conductive rings withone fixed to the yoke assembly and the other rotating with the sphericalpayload. The rings remain in electrical contact with each other as theelevation drive and rotary joint 140 is rotated and provide anuninterrupted electrical interconnection between elements housed insidethe spherical payload assembly 110 and elements housed inside the yokeassembly 105. In addition, the elements inside the yoke assembly 105 arein communication with the radio transceiver 705 which is carried by theUAV or other support structure 145.

Referring to FIG. 10, the electrical subsystems housed inside thespherical payload assembly 110 include a payload controller 720, asecondary drive system controller 725, and additional electricalcomponents and or sub systems that are associated with the three videocameras 310, 315, 335, and with the laser target designator and laserrangefinder systems. The payload controller 720 interfaces with all ofthe electrical components and sub systems housed inside the sphericalpayload assembly 110 to control the operation of the spherical payloadassembly 110 and communicate with electrical subsystems not housedinside the payload assembly 110 through the slip ring assembly 330. Inparticular, payload controller 720 includes a first microprocessor forcontrolling the primary camera and for reading out video data from theprimary focal plane array. The payload controller 720 also controlsoperations of and data processing and communication related to the lasertarget designator module 345 and laser rangefinder transmitter module340.

Referring to FIGS. 10 and 11, the electrical subsystems housed insidethe yoke assembly 105 included four circular PCB's 750, 755, 760, 765configured to fit within the electronics cavity 160 stacked one aboveanother and electrically and mechanically interconnected. In addition,the electrical subsystems housed inside the yoke assembly 105 include aplurality of power supplies 730 disposed around the upper bracket 165and a power supply 735 disposed in the yoke arm 215. The electricalsubsystems housed inside the yoke assembly 105 also include an azimuthmotor driver 740 which is disposed inside the electrical cavity 160attached to the thin annular wall 155 proximate to the upper bracket 165and an elevation motor driver 745 disposed in the yoke arm 210.

The four circular PCB's include a primary servo controller 750, forcontrolling the pointing direction of the primary pointing axis 130, avideo encoder 755, for compressing video data from all three camerasystems, a master controller 760, for receiving video data from allthree camera systems and communicating the video data from two images ata time to an Ethernet switch 816 and associated communication processor820, and a dual channel tracker 765, which includes a primary channelfor tracking the primary pointing axis 130 and a secondary channel fortracking the secondary pointing axis 332.

The payload controller 720 includes a commercially available fieldprogrammable gate array (FPGA), not shown, e.g. manufactured by XILINIXInc. of San Jose Calif., USA. In addition, the payload controller 720includes a digital microprocessor, e.g. a Power PC 405, memorycomponents, at least comprising short term memory registers, a clocksignal or timing generator, and other components as may be required toperform operations according to program steps operating on the FPGA. Thepayload controller 720 further includes additional non-volatile memorydevices such as flash memory and electrically erasable programmablememory (EEPROM) for storing the program steps and other data which maybe loaded into the FPGA on power up and used to manage the operation ofelements housed inside the spherical payload assembly 110 and toexchange data and commands with the master controller 760 through theslip ring assembly 330. The payload controller 705 further includes auniversal asynchronous receiver/transmitter (UART) used to serializedata exchanged between the payload controller 720 and the mastercontroller 760, as well as other input and output serial communicationchannels such as a joint test action group JTAG connector interfacedwith the Power PC 405 for outputting test and raw data to a test device814, and a state machine operating on the FPGA for controlling each ofthe laser target designator module 345 and laser rangefinder transmittermodule 340.

The payload controller 720 operates to generate clock signals which arecommunicated to the primary camera 310 in order to initiate readouts ofprimary focal plane array according to a frame rate. The second andthird cameras 315 and 335 include clock signal generators and readoutelectronics within the camera systems. The primary video camera 310 andthird video camera 335 are operated with a frame rate of approximately60 Hz and the secondary video camera 315 is operated with a frame rateof approximately 30 Hz. Video data from the video camera 310 is read outand serialized by the payload controller FPGA before being sent to themaster controller 760 in RS 422 format.

The payload controller 720 further operates to exchange commands andstate data with each of the three video cameras 310, 315, 335. Thecommands and state data may comprise on/off commands, camera system modeor state change commands, camera system status updates, and otherconditions of the camera systems such as temperature, power usage,illumination levels, etc. In addition, the payload controller 720communicates with the IDCA 370 and the telescope 350 to control andmonitor their operating states.

Referring to FIGS. 12 and 15A-B, the flow of video data through thepayload electrical control system 700 is shown in schematic view.Starting with the primary video camera 310 video, primary camera dataframes are read out directly to the payload controller 720 whichserializes the primary data frames and delivers them to the mastercontroller 760 over a first video channel 761. The master controller 760includes a first digital processor 804 such as a field programmable gatearray, (FPGA) that receives the serialized primary data frames from thepayload controller 720 and makes offset/gain and dead pixel replacementcorrections and then outputs the corrected serialized primary dataframes to the video encoder PC board 755 for data compression and to thetracker PC board 765 for tracking and meta data generation. The videoencoder PC board 755 includes a third digital processor such as adigital signal processor, (DSP) or application specific integratedcircuit (ASIC) 806 mounted thereon. The third digital processor 806compresses the corrected serialized primary data frames and deliverscompressed corrected primary data frames to the Ethernet switch 816which operates in cooperation with the specialized communicationsprocessor 820 to packetize the primary data frames with each data packetbeing addressed to the first IP address associated with the remotestation 710 before communicating packetized data to the radiotransceiver 705. Alternately, the FPGA 804 may communicate uncompressedvideo data directly to the Ethernet switch 816 e.g. by disabling videodata compression programs running on the third digital process 806. Asecond output channel from the FPGA 804 delivers the serialized primarydata frames to a primary tracker 808 mounted on the dual channel trackerPC board 765. The primary tracker 808 generates tracking meta datarelated to the primary data frames and delivers the primary trackingmeta data to the communications process 820 which packetizes the primarytracking meta data with each data packet being addressed to the third IPaddress associated with the remote station 710 before communicatingpacketized primary tracking meta data to the radio transceiver 705.

With respect to the secondary video camera 315 and the tertiary videocamera 335, data frames from the selected camera 315 or 335 are passedthrough multiplexor mounted on the payload controller 720 to the mastercontroller 760 which includes a second digital processor 812 such as anFPGA that receives the serialized data frames from the payloadcontroller 720 and, if necessary, makes video corrections and thenoutputs corrected serialized secondary data frames to the video encoderPC board 755 for data compression and to the tracker PC board 765 fortracking and meta data generation. The video encoder PC board includes afourth digital processor 818, such as a DSP or ASIC, mounted on thevideo encoder PC board 755. The fourth digital processor 818 compressesthe corrected serialized data frames of the selected camera and deliversthe compressed data frames from the selected camera to the Ethernetswitch 816, which operates in cooperation with a specializedcommunications processor 820 to packetize the selected camera dataframes with each selected camera data packet being addressed to thesecond IP address associated with the remote station 710 beforecommunicating packetized data to the radio transceiver 705. Alternately,the FPGA 812 may communicate uncompressed video data directly to theEthernet switch 816 e.g. by disabling video data compression programsrunning on the fourth digital processor 818. A second output channelfrom the second digital process 818 delivers the serialized secondarydata frames to a secondary tracker 810 mounted on the dual channeltracker PC board 765. The secondary tracker 810 generates tracking metadata related to the data frames of the selected video camera anddelivers the secondary tracking meta data to the communications process820 which packetizes the secondary tracking meta data with each datapacket being addressed to the third IP address associated with theremote station 710 before communicating packetized primary tracking metadata to the radio transceiver 705.

While the master controller PC board 760 described above includes firstand second digital signal processor 804 and 812 for separatelyprocessing two separate video images, a preferred embodiment utilizes asingle digital video image processor 805 configured to receive videoimage data from the primary video camera 310 and the selected videocamera 315 and 335 and to operate in a multiplex mode to process boththe primary video image and the selected video image and to deliver theprimary video data to the third digital processor 806 for compressionand the primary tracker 808 for tracking and to deliver the selectedvideo image to the fourth digital processor 818 for compression and tothe secondary tracker 810 for tracking.

Accordingly, when the primary and secondary video cameras are selectedfor viewing the Ethernet switch 816 in cooperation with thecommunications process 820 merges the primary video image addressed tothe first IP address, the secondary video image, from the second videocamera 315 addressed to the second IP address, and the tracking metadata addressed to the third IP address into a single packetized networkdata stream such that the payload system 100 simultaneously communicatestwo display formatted video images and a meta data file to the radio 705for transmission to the remote station 710 associated with the firstsecond and third IP addresses.

Similarly, when the primary and tertiary video camera are selected forviewing the Ethernet switch 816 in cooperation with the communicationsprocess 820 merges the primary video image, addressed to the first IPaddress, the tertiary video image from the third video camera 335,addressed to the second IP address, and the tracking meta data addressedto the third IP address into a single packetized network data streamsuch that the payload system 100 simultaneously communicates two displayformatted video images and a meta data file to the radio 705 fortransmission to the remote station 710 associated with the first,second, and third IP addresses.

Preferably, the network packetized data stream is configured with awireless Ethernet network protocol, however, any other wireless protocolsuitable for transmission over the onboard radio 705 is usable withoutdeviating from the present invention. In addition, each of the DSP's 806and 818 delivers compressed video data to a scaling and overlayprocessor 822 operating on the master controller 760. The scaling andoverlay processor 822 prepares the video data for local display, e.g.when the UAV is on the ground and or being used in evaluation in testmode e.g. on the test station 814. Alternately, uncompressed video canbe delivered to the local display.

The communication processor 820 may include a specialized datacommunications processor such as a MPC8247: Power QUICC II IntegratedCommunication Process manufactured by Freescale Semiconductor of AustinTex., USA. The data communications processor combines a core digitaldata processor, such as a PowerPC 603, and a RISC based communicationprocessor with internal memory elements, a clock signal generator, andvarious interface and control modules and is programmed to operate incooperation with the Ethernet switch 816 or another network switch. Eachof the video compression DSP's 806 and 818 communicates video data tothe Ethernet switch 816 and each of the trackers 808 and 810communicates tracking meta data to the communication processor 820 andthe data from both sources is merged in the network packetized datastream described above. In an alternate embodiment, a fourth IP addresscan be used to deliver tracking meta data associated with each of thevideo images to separate a IP address.

Referring now to FIG. 11, the circular PC boards 750, 755, 760 and 765are shown in exploded view with electrical and mechanical interfacehardware shown in detail. Each circular PC board has an outsiderdiameter defined by a circular peripheral edge 855 and opposing top andbottom opposing surfaces. The outside diameter is sized to substantiallyfill the inside diameter of the thin annular wall 155 and the circularPC boards are assembled together as a stack and installed into thehollow electrical cavity 160 with the top and bottom surfaces of each PCboard substantially normal to the azimuth axis A.

Each circular PC board includes a plurality of thermally conductive pads850, such as an exposed copper layer of the PC board, disposed equallyspaced around its peripheral edge 855 on top and bottom surfacesthereof. More specifically each PC board includes an internal layer ofcopper or other thermally conductive material substantially over itsentire area and the conductive pads 850 are exposed portions of theconductive internal layer. A plurality mounting blocks 860 are disposedbetween opposing PC boards at locations corresponding with theconductive pad 850. In addition, a plurality of bottom mounting blocks865 are disposed at locations corresponding with conductive pads 850formed on the bottom surface of the bottom PC board 765. Each mountingblock comprises a thermally conductive material or otherwise provides athermally conductive path through the mounting block. In addition, aplurality of thermally conductive and electrically insulating spacersmay be disposed between the conductive pads 850 and the mounting blocks860 and 865 between the PC boards and the mounting blocks.

Each mounting block 860 as well as each conductive pad 850 and eachspacer 870 includes a through hole 875 passing through the block,conductive pad or spacer. The through holes are substantially parallelwith the azimuth axis A, or longitudinal, and a plurality oflongitudinal mounting screws 880, one corresponding with each conductivepad location, installs through the aligned holes 875 and engages with athreaded hole 880 formed in each bottom mounting block 865 such that thelongitudinal mounting screws 880 align the PC boards with the mountingblocks 860 and 865 and providing a longitudinal clamping force thatclaims the PC boards between opposing mounting blocks into a stackseparated by mounting blocks 860 and spacers 870 so that a substantiallycontinuous thermally conductive path extends longitudinally along eachlongitudinal mounting screw 880 to allow thermal energy to be conductedbetween PC boards to prevent local overheating. In addition some of thePC boards may include a center through hole defined by an inner diameter894 as may be required to avoid contact with other elements such ascomponents of the azimuth drive and other longitudinal mounting screws885 may pass through the PC boards and through hollow spacers 890disposed between PC boards to further secure the PC boards in place andincrease mechanical stiffness of the PC board stack.

In addition to assembling the plurality of PC boards 750, 755, 760, 765into a stack using mounting longitudinal screws 880 and 885, the PCboards are electrically interconnected with each other using a pluralityof multi-pin connectors 895 and electrically connected with otherelectrical systems using one or more edge connectors 900. Thereafter,the entire stack may be lowered into the hollow electrical cavity 160and a plurality of threaded nuts 905 disposed to mate with each of themounting blocks 860 and 865 are aligned with corresponding through holes910, shown in FIG. 10, formed to pass through the thin annular wall 155such that mounting screws, not shown, can be installed through each hole910 and each mounting block 860 and 865 to engage with each threadednuts 905 to support the stack of PC boards 750, 755, 760, 765 inside thehollow electrical cavity 160.

According to the present invention, thermal energy generated by each ofthe PC boards 750, 755, 760, 765 is thermally conducted by theconductive internal layer along radial paths to each of the conductivepads 850 to each of the mounting blocks 860/865 and then to the thinannular wall 155 which is exposed to external airflow. The excessthermal energy is then dissipated by the convective and radiant heattransfer between the thin annular wall 155 and the external airflow.

It will also be recognized by those skilled in the art that, while theinvention has been described above in terms of preferred embodiments, itis not limited thereto. Various features and aspects of theabove-described invention may be used individually or jointly. Further,although the invention has been described in the context of itsimplementation in a particular environment, and for particularapplications, those skilled in the art will recognize that itsusefulness is not limited thereto and that the present invention can bebeneficially utilized in any number of environments and implementationsincluding but not limited to payload systems that include fewer or moreelectro-optical systems or combinations thereof. Accordingly, the claimsset forth below should be construed in view of the full breadth andspirit of the invention as disclosed herein.

The invention claimed is:
 1. An optical payload comprising: amid-infrared primary video camera for imaging a target with respect to aprimary point axis of the camera, the camera including a folded narrowfield of view fixed first magnification telescopic optical system havinga telescope optical axis that is not parallel to the primary pointingaxis; and a folded cryocooler formed integrally with the primary videocamera for cooling a primary focal plane array to an operatingtemperature below 90° K, wherein the folded cryocooler includes a rotaryDC motor for driving both a gas compressor piston and a regeneratorpiston through a folded linkage and wherein the folded linkagereciprocally drives a regenerator piston along a linear axis that isparallel with a rotation axis of the DC motor.
 2. The optical payload ofclaim 1 wherein the folded narrow field of view fixed magnificationtelescopic optical system comprises two fold mirrors each disposed at acompound angle with respect to the primary pointing axis, and whereinthe mid-infrared primary video camera includes an actuator configured tomove along the telescope optical axis to actuate the first magnificationtelescopic optical system to focus an image on the primary focal planearray.
 3. The optical payload of claim 2 wherein the folded cryocoolercomprises a rotary DC motor for driving a gas compressor and a foldedlinkage, each housed inside a crankcase, and wherein the folded linkagereciprocally drives a regenerator piston along a linear axis that isparallel with a rotation axis of the DC motor.
 4. The optical payload ofclaim 3 further comprising a secondary video camera including a fixedmagnification wide field of view optical system for forming a secondaryimage of the target onto a secondary focal plane array at a secondmagnification, that is less than the first magnification, wherein thesecondary focal plane array comprises elements suitable for renderingthe secondary video image over a long-infrared spectral range.
 5. Theoptical payload of claim 4 further comprising: a cylindrical yokeassembly rotatably attached to a support structure for housing a firstportion of a payload electrical control system in a cylindrical topsection of the yoke assembly that is formed by a thin annular wallsurrounding a hollow electronics cavity that includes a circular topopening for installing electrical control systems therein; a sphericalpayload assembly rotatably attached to the yoke assembly for housing theprimary video camera, the folded cryocooler, the secondary video cameraand a second portion of the payload electrical control system therein;and a primary drive system configured to rotate the yoke assembly aboutan azimuth axis (A) and to rotate the spherical payload assembly aboutan elevation axis (E) for pointing the primary pointing axis.
 6. Theoptical payload of claim 5 further comprising a slip ring assemblydisposed between the payload assembly and the yoke assembly forexchanged electrical signals there between.
 7. The optical payload ofclaim further comprising a plurality of circular PC boards each having acircular peripheral edge and opposing top and bottom surfaces populatedwith surface mounted electrical components and electrical connectors,wherein each of the plurality of circular PC boards is disposed withinthe circular cavity with top and bottom surfaces thereof substantiallynormal to the azimuth axis (A).
 8. The optical payload of claim 7further comprising a plurality of mounting blocks fixedly attached tothe thin annular wall and disposed to contact thermally and electricallyconductive pads formed on each of the plurality of PC boards wherein themounting blocks fixedly supporting each of the plurality of PC boardsinside the hollow cavity and provide a thermally and electricallyconductive path between each of the plurality of PC boards and the thinannular wall.
 9. The optical payload of claim 8 further comprising: alaser rangefinder transmitter module comprising a rangefinder laser foremitting a pulsed laser rangefinder beam and a small aperture telescopiclens system configured to substantially collimate and point the laserrangefinder beam at the target; and a laser target designator modulecomprising a designator laser for emitting a pulsed laser targetdesignator beam, a large aperture telescopic lens system configured tosubstantially collimate and point the designator beam at the target, alaser rangefinder receiver module for generating a photocurrentresponsive to an energy of the pulsed laser range finder beam fallingthereon, first optical elements disposed along a first optical pathbetween the large aperture telescopic lens system and the designatorlaser for directing the pulsed laser target designator beam from thedesignator laser to the large aperture telescopic lens system; andsecond optical elements disposed along a second optical path between thelarge aperture telescopic lens system and the laser rangefinder receivermodule for directing an energy of the a pulsed laser rangefinder beamthat is reflected by the target area and collected by the large aperturetelescopic lens system onto an active area of the laser rangefinderreceiver module.
 10. The optical payload of claim 4 further comprising athird video camera including an optical system for forming a tertiaryimage of the target, wherein the third video camera is configured torender the tertiary video image of the target area over a visiblespectral range.
 11. The optical payload of claim 4 further comprising:area master controller for correcting a primary video image of thetarget area and a secondary video image of the target; a network switchfor receiving each of the corrected primary and secondary video imagestherein; and a communication processor in communications with a networkswitch for merging the corrected primary and secondary images into asingle network packetized data stream suitable for transmission over aradio transceiver wherein data packets associated with the primary videoimage are addressed to a first IP address and data packets associatedwith the secondary video image are addressed to a second IP address. 12.An optical payload comprising: a mid-infrared primary video camera forimaging a target with respect to a primary pointing axis of the camera,the camera including a folded narrow field of view fixed magnificationtelescopic optical system having a telescope optical axis that is notparallel to the primary pointing axis; a folded cryocooler formedintegrally with the primary video camera for cooling a primary focalplane array to an operating temperature below 90° K, the foldedcryocooler including a rotary motor driving both a compressor piston anda regenerator piston, wherein the rotary motor drives the regeneratorpiston through a linear axis that is parallel with a rotary axis of therotary motor; a long-infrared secondary video camera including a fixedmagnification wide field of view optical system for forming a secondaryimage of the target; and a visible-light third video camera including anoptical system for forming a tertiary image of the target.
 13. Theoptical payload of claim 12 further comprising: a laser rangefindertransmitter module comprising a rangefinder laser for emitting a pulsedlaser rangefinder beam directed at the target; a laser rangefinderreceiver module for generating a photocurrent responsive to an energy ofthe pulsed laser rangefinder beam that is reflected by the target areaand directed onto an active area of the laser rangefinder receivermodule; and a signal processor in communication with the laserrangefinder receiver module for processing photo current signalsgenerated in response to the energy of the pulsed laser rangefinder beamthat is reflected by the target to determine a range between the opticalpayload and the target, wherein the mid-infrared primary video cameraincludes an actuator configured to move along the telescope optical axisto actuate the folded narrow field of view fixed magnificationtelescopic optical system to focus an image on the primary focal planearray.
 14. The optical payload of claim 13 further comprising a lasertarget designator module comprising a designator laser for emitting apulsed laser target designator beam directed at the target.
 15. Theoptical payload of claim 14 wherein the laser target designator modulecomprises: the designator laser; the laser rangefinder receiver module;a large aperture telescopic lens system configured to substantiallycollimate and point the designator beam at the target and to collect theenergy of the pulsed laser rangefinder beam that is reflected by thetarget; the signal processor for processing photo current signalsgenerated thereby to determine a range between the optical payload andthe target first optical elements disposed along a first optical pathbetween the large aperture telescopic lens system and the designatorlaser for directing the pulsed laser target designator beam from thedesignator laser to the large aperture telescopic lens system; andsecond optical elements disposed along a second optical path between thelarge aperture telescopic lens system and the laser rangefinder receivermodule for directing the energy of the a pulsed laser rangefinder beamthat is reflected by the target and collected by the large aperturetelescopic lens system onto the laser rangefinder receiver module. 16.The optical payload of claim 15 wherein both the first optical elementsand the second optical elements include a beam splitter configured totransmit the laser target designator beam and to reflect the energy ofthe pulsed laser rangefinder beam that is reflected by the target. 17.The optical payload of claim 16 wherein the first optical elementsfurther comprise two mirrors disposed between the beam splitter and thelarge aperture telescopic lens system.
 18. The optical payload of claim17 wherein the second optical elements further comprise a mirror and afocusing lens set for focusing the energy of the pulsed laserrangefinder beam that is reflected by the target area onto an activearea of the laser rangefinder receiver module.
 19. The optical payloadof claim 18 wherein the beam splitter comprises a dichroic filterconfigured with a maximum spectral transmission substantially matchedwith a spectral emission of the designator laser and further configuredwith a maximum spectral reflectance substantially matched with thespectral emission of the rangefinder laser.
 20. The optical payload ofclaim 19 further comprising a fiber optic element extending between thelaser rangefinder transmitter module and the laser designator module fordirecting at least a portion of the energy of each pulse of the laserrangefinder beam onto an active area of the laser rangefinder receivermodule.
 21. The optical payload of claim 20 further comprising: acylindrical yoke assembly rotatably attached to a support structure forhousing a first portion of a payload electrical control system in ahollow cylindrical top section thereof; a spherical payload assemblyrotatably attached to the yoke assembly for housing the primary videocamera, the folded cryocooler, the secondary video camera, the thirdvideo camera, the laser rangefinder transmitter module, the laser targetdesignator module and a second portion of the payload electrical controlsystem therein; and a primary drive system configured to rotate the yokeassembly about an azimuth axis (A) and to rotate the spherical payloadassembly about an elevation axis (E) for pointing the primary pointingaxis at the target.
 22. The optical payload of claim 21 wherein thespherical payload assembly is formed with a spherical external housinghaving a housing outside diameter of less than 190 mm.